document.write ("<b>上一篇</b>：<a href='/DocHtml/699/2014/3/3/4078611034646.html'>用字母表示</a><br><b>下一篇</b>：<a href='/DocHtml/699/2014/3/1/5110227234644.html'>§1.2数轴、相反数和绝对值</a>")